


Adoption by Kidnapping

by Seito



Series: Adoption by Kidnapping [1]
Category: Katekyou Hitman Reborn!, 天空侵犯 | Tenkuu Shinpan
Genre: Chaos, Crack, Humor, Kid Fic, M/M
Language: English
Status: Completed
Published: 2017-07-07
Updated: 2017-07-07
Packaged: 2018-11-28 23:25:09
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,318
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11428431
Author URL: https://archiveofourown.org/users/Seito/pseuds/Seito
Summary: In which Tsuna frets, Reborn is amused and their little sniper manages to inherit some of his fathers’ more troublesome habits.Sniper-Mask-is-Reborn-and-Tsuna’s-kid!AU(Do not need to know Tenkuu Shinpan in order to read this)





	Adoption by Kidnapping

**Author's Note:**

> You do not need to read Tenkuu Shinpan to understand this fic. That said, there's a minor spoiler regarding Sniper Mask's name. So turn around if you don't want to know. Otherwise, if you're familiar with the manga and/or follow me on tumblr, you know I've been cackling over the fact that [Sniper Mask](http://seitosokusha.tumblr.com/post/162519014868/seitosokusha-meet-my-new-favorite-character) looks exactly like Reborn. Thus the idea of writing a kid fic came to life ahaha
> 
> Sniper Mask -> Yu  
> Edit: Double checking against the raws, I apparently have Sniper's name backwards. >> So it has been corrected.

Reborn looked down at the scene in front of him. It hadn’t changed. There were still two heads instead of one in his son’s bed. Yu was curled around a smaller black haired boy, both sound asleep and unaware of Reborn’s presence. 

Leaving Leon on the side table, Reborn turned around and went to hunt down his husband. 

Predictably, Tsuna was still locked up in his office, grumbling at the paperwork. 

“Your son,” Reborn drawled, “Is taking after your bad habits.” 

Tsuna’s gaze shot up. “What is that supposed to mean?” he demanded. “What has Yu done now? And -” he looked at the clock, frowning at the time, “-shouldn’t he be asleep? Wait, did I not wish him goodnight?” Tsuna panicked. 

“He knew you were busy, that we’re both busy and he, according to the maids, didn’t want to bother us and went straight to bed without any fuss,” Reborn said. “But clearly he had an ulterior motive, given that he snuck in a stray.” 

“A pet?” Tsuna asked, confused. 

“No, a human,” Reborn said. “He’s curled around another kid.” 

“He kidnapped someone?” Tsuna blurted out. “He’s only eight! He’s too young to kidnap someone!” 

“I don’t see the other kid protesting,” Reborn said. 

“This isn’t something to be amuse about Reborn!” 

-.-.-.-.-.-

The other kid’s name was Honjo Rika. 

“Rika is staying with us,” Yu said with the certainty of a child, the following morning. He stood with Rika, hands intertwined. Rika yawned, rubbing his eyes, dressed in a pair of borrowed pajamas from Yu. 

Tsuna let out a nervous laugh. “Yu-chan,” he said gently. “I think Rika will need to go home eventually. I’m sure he has family that will miss him.” 

Rika nodded his head. “Yuri is waiting,” he said. 

Yu pouted and gripped Rika’s hand tighter. 

Tsuna mentally cooed. His son was so cute, but impromptu sleepover aside, kidnapping wasn’t well… okay, fine, it was technically acceptable in this household, just not at Yu’s age! 

More importantly, now that Tsuna had time to sleep on the idea, he was ecstatic that Yu had made a friend his age. Yu hadn’t shown any interest in other kids before. Granted, being Tsuna and Reborn’s son made finding playdates a little hard, but Yu had always been content to read his books or follow Reborn around. 

For Yu to have brought home a friend was nothing short of a miracle in Tsuna’s books. 

Next to Tsuna, Reborn merely rolled his eyes and sipped his coffee. 

Neither of them knew that this was just the start. 

-.-.-.-.-.-

Reborn tugged at his tie, loosening it as he trekked down the long hallway. He couldn’t wait until this month was over. Every year Vongola was in charge of throwing a ball with all of its allies. It was a large and grand affair, steep in tradition, a time to renew bonds and friendships. 

It was also a security and logistical nightmare. 

He turned left, heading towards Yu’s bedroom, determined to see his son in bed before turning in himself (after dragging Tsuna off to sleep.) 

To his surprise, Tsuna was already standing at the doorway of Yu’s bedroom, frowning. 

“What’s wrong?” Reborn asked. 

Tsuna glanced at him. “They’re multiplying,” he hissed. 

Reborn glanced inside. Sure enough there were three heads in Yu’s king sized bed this time. Yu was curled around Rika who was snugged in the middle. On the other side of Rika was a smaller girl, similar to Rika in features. 

“Honjo Yuri,” Reborn said. Apparently this was Rika’s little sister. 

“Where is he finding them?” Tsuna despaired. “I mean I should be happy that Yu-chan is finally gaining his own set of friends. But, where are they coming from?” 

The other problem with the Vongola Ball was both Reborn and Tsuna became so swamped with work, that they didn’t get to see Yu as often as they liked. It wasn’t much of an issue when they first brought him home, but he was growing up in leaps and bounds, going to bed without any bedtime stories and apparently, bringing over friends for impromptu sleepovers. 

“We can always ask Viper to look into it,” Reborn said. 

He also made a mental note to correct this large security hole. It was one thing if Yu had snuck in a friend and everyone was busy enough to have missed it. It was another if he had done it twice and no one thought to alert Tsuna or Reborn. 

-.-.-.-.-.-

“This is Yuri,” Yu introduced the small girl the following morning at breakfast. “Both Rika and Yuri are staying here.” 

Tsuna looked at Reborn. 

Reborn sipped his coffee. “He learned to bring home strays from you,” Reborn said, clearly not helping. 

Tsuna frowned. “I remember it as a certain someone barging into my life and dragging everyone else in, kicking and screaming,” he deadpanned. He turned back to his son. “Yu-chan, I’m sure Rika and Yuri’s parents will miss them very much.” 

“We don’t have any,” Rika said. 

“Mommy and Daddy went away,” Yuri said. “They haven’t come back in a long time.” 

Tsuna shared a look with Reborn. Orphans? Drats, Tsuna had a soft spot for orphans. Reborn wasn’t going to let him live this down. 

-.-.-.-.-.-

“I’m supposed to be happy right?” Tsuna asked. He was hiding from his paperwork in Dino’s mansion. If he had to look at another Vongola Ball related piece of paperwork today, he was going to burn something down… which would only make even more paperwork for him. “Yu-chan is finally making friends.” 

Dino patted him on the back and handed Tsuna a cup of black coffee. “He was such a prickly child. Just like Reborn.” 

Tsuna let out a bark of laughter. “He’s trying to mimic Reborn. Hasn’t given up on it, actually. He thinks Reborn is the ‘coolest’ thing he knows.” 

“Wait, really?” Dino asked. “Huh, I mean if I didn’t know, I would have assumed that Yu was Reborn’s child by blood. They act alike. Actually I assumed that was the reason why Yu had resorted to kidnapping his friends. He decided that he liked them enough that he simply took them from the orphanage they were living in. It was a very Reborn thing to do.” 

Tsuna set his cup down to bury his head in his hands. “He’s too young to be kidnapping people, Dino-nii! I’m trying to stop things like child-kidnapping in the mafia,” he wailed. 

“There, there. I’m sure it’s only those two,” Dino said. 

It wasn’t. 

-.-.-.-.-.-

“Yu-chan,” Tsuna said, voice strained. 

Yu gave him a shifty look, not quite meeting his father’s eyes. 

Tsuna took a deep breath, centering himself. “Yu, why are all the kitchen knives missing?” 

In a desperate search for coffee, Tsuna had personally gone to the kitchen for a cup instead of waiting for someone to bring him some. As he had entered, he had saw Yu scrambling out the other entrance and all the knife drawers suspiciously empty. 

Tsuna had a small heart attack at the mere thought of his son handling several very sharp and very dangerous knives by himself. 

Yu might want to take after Reborn, but he was still a young child and Tsuna easily caught the way Yu glanced over to the couch. Tsuna walked over to the couch, and peered behind it. There, armed with all the kitchen knives was a small blond haired girl who immediately threw a knife at Tsuna. 

Tsuna caught it with practiced ease, reaching out with his other hand to pick up the girl by her collar. He disarmed her of her other knife with a flick of his wrist. “Yu,” Tsuna said, looking back at his son. 

“She’s Nise Mayuko,” Yu said, his face set in a familiar line of determination. “I found her. She’s staying.” 

“Yu,” Tsuna said gently. “You can’t just kidnap people and bring them back here because you want to.” 

Yu frowned. “But you and Papa do it all the time.” 

Tsuna let a strangled laugh. Of all the habits that Yu had to pick up from him and Reborn. 

-.-.-.-.-.-

“The Varia want her,” Xanxus said, strolling into Tsuna’s office. Thrown over his shoulder was Mayuko who was kicking and pounding.

“Let me go!” Mayuko said, punching Xanxus’ shoulder. 

“No, Xanxus,” Tsuna said, halfway horrified. 

“She’ll fit right in,” Xanxus said. “Bel will fucking love training her. She’s fucking knife nut like him.” 

“No,” Tsuna repeated. Because if nothing else, Yu had proven to be overly protective of his new friends (who haven’t left or returned to their former homes because curse his soft heart, Tsuna couldn’t return them to the orphanage or streets to where Yu had found them). 

Right on cue, Yu burst in and fired his gun at Xanxus who dodged it. Rika darted forward, sweeping a broom at Xanxus’ feet as Yuri jumped at the same time, armed with a water balloon and threw it at Xanxus’s face. The combination attack was just enough that Xanxus stumbled, his grip on Mayuko loosen, allowing her to get free. 

The four kids scrambled out of the room, running away as fast as they could. 

There was a beat of silence as both Xanxus and Tsuna stared at the doorway where the kids had vanished. 

“Trash,” Xanxus said soft but deadly tone, pushing back his wet hair. “I want them all.” 

“No, Xanxus,” Tsuna said. “Absolutely not. Yu is only eight! The rest of them are even younger!”

“That’s the best time to train them, trash!” 

“Xanxus!” 

“Baby boss is already on his way to being a sniper just as good as the fucking hitman.” 

“That’s not the point Xanxus!” 

-.-.-.-.-.-

Tsuna blinked, watching his son play with his friends. He couldn’t believe it had been two weeks since Yu had brought them all home. 

“You look tired,” Reborn stated, handing Tsuna cup of coffee. 

“This Vongola Ball is going to be a nightmare,” Tsuna said, utterly numb at this point. One would think it would get easier given how often they did it, but it always seemed to get worse. He was purposely not looking at anything today. 

“It’ll be over in two weeks,” Reborn said. 

Tsuna drowned his cup of coffee, shoulders relaxing at the taste of the hot liquid. He couldn’t wait until it was over. This time of year was always a bundle of extra stress. Head pounding, he pushed back the millions of things still left to do, choosing to focus on his son instead. He watched as Yu hugged Rika, Rika leaning back in the embrace. 

“Yu-chan is downright affectionate with Rika-kun,” Tsuna said, blinking. Mostly out of his very brief stint as an orphan, Yu had always shied away physical affection. It was a little surprising to see how often he clung to Rika. 

“Hmm, the first Element you harmonize with tends to be special,” Reborn said mildly. “Most Skies marry their first Element.” 

Tsuna chuckled. “It’s a good thing Hayato and I-” he cut himself off, sitting up straighter, more alert. He turned to look at Reborn, eyes wide. “Even back then?” Tsuna whispered. 

Reborn’s gaze remained fixed on their son. “Dame-Tsuna,” he said, tone full of fond exasperation and love. 

Tsuna felt his heart squeeze with joy as he stared at his husband in reverence. He smiled, bright and wide. “I love you too.” 

-.-.-.-.-.-

“Who is this?” Reborn asked, tilting his head up to lift the brim of his fedora. 

Yu glanced back at the small light green haired girl hiding behind him. “This is Shinzaki Kuon. I want her to stay?” he trailed, off a little skeptical. 

Kuon peeked out from behind Yu, her hands gripping tight to Yu’s sleeve. She was a small and tiny girl, reminding Reborn of Yuni. 

“And where did you find her?” Reborn asked, eyebrow raising. 

“In a house,” Yu hedged. 

“I-I don’t want to go back!” Kuon protested. 

Reborn’s eyebrow raised even higher. “I hope you didn’t sneak into the Shinzaki Mansion especially considering the Shinzaki Famiglia is one of Vongola’s enemies and you are currently Vongola’s _only_ heir.” 

Yu didn’t even flinched, but Reborn could easily read the guilt. “Don’t tell tousan?” Yu asked. 

“You’re grounded,” Reborn said. 

-.-.-.-.-.-

“What do you mean the Shinzaki Famiglia might attack us?” Tsuna asked in disbelief. 

“We have their heir,” Reborn answered. 

“Why do we have their heir?!”

“Because Yu decided to kidnap her and bring her here,” Reborn said; a smirk curling on his face. “It seems he took a leaf out of your book and made his enemy a friend.” 

Tsuna made a low pitched noise before reaching out to punch Reborn’s shoulder. “It’s not funny,” he said. “Why did he have to pick up your love of causing chaos?” 

Reborn, who had lazily caught Tsuna’s punch, smirked. “I think it's rather fitting.” 

-.-.-.-.-.-

The five children had been inseparable. Tsuna fretted in the background, but didn't have any heart to send them away, back to the cold streets or unloving homes. Reborn was several degrees of amused, poking at the children and pleased by their reactions as they steady climbed up to his expectations. 

Tsuna’s Guardians thought they were the _best thing ever_. 

-.-.-.-.-.-

“We’re taking Kuon-chan,” Mukuro said, strolling into Tsuna’s office. 

Tsuna looked up from his paperwork, alarmed. “No, Mukuro.” 

“Kufufu, too late. Chrome is already teaching her,” Mukuro said. “She has quite the gift with Mist Flames.” 

“Mukuro if she comes back with a pineapple hairstyle, I will let Reborn kill you.” 

-.-.-.-.-.-

“Kyoya,” Tsuna huffed tiredly. He had thought his Cloud Guardian was purposely hanging around more the mansion.

Kyoya said nothing, looking stoically at Tsuna. 

“Please stop providing Mayuko-chan with knives,” Tsuna stressed. Mukuro had been winding Kyoya up again, taunting him over how Mukuro and Chrome were teaching Kuon. Kyoya, of course, took it as a challenge and set out to find his own student. He picked Mayuko. Mayuko was just happy enough to have a steady supply of knives. 

“Hn.” 

Tsuna let out a strangled noise and refused to bury his head in hands. Sooner or later a three way fight was going to break out between Bel, Xanxus and Kyoya over who got to train her. 

-.-.-.-.-.-

There was a loud crash and Tsuna twitched, already mentally calculating the cost of the potential damages. 

He swiftly left the room, breaking out into a run as the sound of gunshots rang down the hallway. A jolt of fear struck his heart, immediately worried. 

“What is going on here?” Tsuna roared, bursting into the room. His Sky Flames were lit, orange eyes glowing as he looked around. 

Everyone froze, staring at him. Verde stood on one end of the room with Rika in hand. On the other side, Yu and Yuri were armed with guns. Kuon was carrying the trident Mukuro got her and Mayuko had far too many knives in her hands. 

Verde straighten his jacket and pushed his glasses up his nose. “Tsunayoshi, Honjo-kun here has an excellent source of Lightning Flames and a brilliant brain.” 

“He’s trying to take away Rika, tousan,” Yu called out. 

Tsuna took a deep breath. This wasn’t what he expected and Verde should have known better. This was the not the month to be giving Tsuna extra paperwork. 

“You’re all grounded,” Tsuna said. “There will be no desserts tonight and I want all your weapons. This includes you Verde.” 

“Tousan!”

“You can’t ground me, Tsunayoshi.” 

Tsuna twitched, the ice of Zero Point Breakthrough gathering in his fist. “So help me, Verde, you will listen to me.” 

Verde wisely did. 

-.-.-.-.-.-

“Hayato,” Tsuna said tiredly. 

“What can I do for you, Juudaime?” Hayato quickly stood at attention. 

Tsuna made a soft noise deep in his throat. Surrounding Hayato was Yu and his friends, poking at what better not be a live bomb. Rika was armed with a pair of pliers, tracing the lines of wire, trying to figure out which one would disable it. 

“Hayato, why are you teaching them how to disarmed a bomb?” Tsuna asked, already dreading the answer. 

Hayato looked down at the kids and back at Tsuna. “It’s good to know! You never know when you need to disable a bomb, Juudaime.” 

Tsuna cast his gaze upward and counted to ten. 

-.-.-.-.-.-

“I don’t know why I’m surprised by this,” Tsuna said mildly. 

Explosions went off in the distance. Mayuko let out a colorful shout which Tsuna was going to let slide, only because he had been in her shoes once. Swearing was the only acceptable response. 

Next to him Reborn smirked. “Nothing builds strong bonds like near death situations,” he said loftily. 

Kuon let out a shriek, followed by gunshots from either Yu or Yuri’s guns. There was a crack of green lightning flames followed by even more swearing. 

“You didn’t even throw me into this training field until I was eighteen,” Tsuna pointed out. 

“They can handle it,” Reborn said confidently. 

-.-.-.-.-.-

Tsuna blamed Reborn for this. 

No matter how much Reborn teased that Yu was taking after Tsuna’s habit of adopting strays, for turning enemies into friends, for being overprotective of his Elements even though they didn’t need it, it didn’t change the fact that between the two of them, Yu picked up the worst possible habit from Reborn. 

Namely the ability to incite chaos without even trying. 

“Well,” Enma said with a laugh as he observed the chaos happening out in the ballroom. “You have to admit, it’s all very Vongola Style.” 

Tsuna let out a weary sigh. “I had hope we wouldn’t destroy the ballroom this year,” he said mournfully. All that paperwork and preparation to ensure that the Vongola Ball would go smoothly went up in a poof of smoke. 

There was a crash and Tsuna watched numbly as his son sniped off Xanxus’ gun. Reborn was in the middle of the chaos, keeping an eye on him. There was another crash as the combined might of Yuri and Mayuko toppled one of Verde’s rampaging machines. Rika darted out of Bel’s range and Kuon threw around a bunch of illusions only to have Mukuro dispel them with lazy ease. 

“VOI YOU IDIOTS! WHAT DO YOU THINK YOU’RE DOING?!” 

A sharp crack and a wall crumbled under the clash attacks of Takeshi and Squalo. Romario got tossed by Koyo, hitting Gamma as he went flying into the refreshment table. 

“Wao~” Byakuran said, whistling and clearly impressed. Yu sniped the chandelier causing to come crashing down on Zakuro. 

Enma laughed. “Well it wouldn’t be a Vongola Ball without something getting destroyed.” 

“They do look like they’re having fun,” Yuni said, eyes twinkling. 

“I hate you all,” Tsuna announced. “You’re absolutely no help.” 

“Think of it this way,” Dino said cheerfully. “Vongola’s next generation is going to be utterly terrifying. Imagine what they can do in twenty years.” 

Tsuna groaned. 

-.-.-.-.-.-

Tsuna tiredly sighed but was unable to stop the small smile from spreading across his face. Reborn dropped a blanket over the three girls as Tsuna tucked Yu and Rika in. 

The ballroom may have been destroyed and the paperwork was going to be a headache tomorrow, but it was nice to have seen how effortlessly Yu and his friends moved as a unit. He was still missing two more Elements, but pride still swelled in Tsuna’s heart. 

Tsuna might fret and worry that they were too young, but he couldn’t deny the swift growing of pride in all five of these children. Perhaps, not the most quiet and peaceful life, but they were thriving and growing. His fingers brushed against Yu’s forehead, smile growing wider. 

“Thank you, tousan,” Yu whispered sleepily before curling tighter around Rika. 

“You’re welcome, Yu-chan,” Tsuna said fondly. “Sleep well.” 

He stepped back, Reborn right behind him. 

“They will go far,” Reborn remarked from the doorway, looking the slumbering children. 

Tsuna nodded. “Yes, yes they will.” 

The future was going to be such a chaotic adventure. 

**Author's Note:**

> This fic didn't turn out as expect. More Tsuna, less Reborn and Yu then originally planned ahaha. But it was fun to write nevertheless. Ahh if this inspired you to read Tenkuu Shinpan, you might want to read this [post of mines](http://seitosokusha.tumblr.com/post/162525801108/araceil-hraap-seitosokusha-but-no) first. It's a pretty graphic for-mature-readers manga. 
> 
> Please leave a review on your way out.


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